Aqueous coating compositions for substrates, such as mineral fiber boards, are becoming increasingly important for both economic and ecological reasons. It is desirable to reduce the use of volatile organic solvents, which can be harmful, resulting in an increased desire for waterborne (i.e., water-based) mixtures. There are, however, some disadvantages associated with the use of waterborne mixtures.
Disadvantages of aqueous solutions include the difficulty, in some cases, of effecting sufficient water dispersibility and solubility of the binder components of the coating composition in water. Where good dispersibility and solubility are achieved, one often encounters lowered resistance of the cured coatings to water. This is less of a problem with coating compositions that are soluble only in organic solvents. In addition, there are processing problems that result from the high viscosity of aqueous coating compositions. These problems have, in some situations, previously been overcome through the use of organic auxiliary solvents in conjunction with water. The use of these auxiliary solvents, however, dampens the economic and ecological advantages of using water in the first place.
One solution, at least as it pertains to coating mineral fiber boards, involves the use of one component waterborne, latex-based coatings. These coatings are based on waterborne latex polymers or polymer solutions including ethylene vinyl chloride, vinyl acrylic, starch, or melamine formaldehyde. Such coatings are either self-crosslinking or coalesce upon drying by use of ovens. Mineral fiber boards are typically used as ceiling tiles and serve to improve thermal and acoustic insulation.
Similarly, two component systems use crosslinking to achieve rapid curing at room temperature without the use of ovens. These two component systems, however, often take up to several hours to cure. Such a limitation on manufacturing and production methods is undesirable, and reduced processing times would be beneficial in many instances.